1. Field of the Invention
The present invention concerns: a method for an end effector of a manipulator—in particular of a robot—to travel a predetermined path; a control device to implement such a method; and a manipulator, in particular a robot, with such a control device.
2. Description of the Prior Art
A typical task of a manipulator is to travel a predetermined path with its end effector. For example, the path can thereby have been predetermined by direct programming (“direct teaching”), i.e. the manual guidance of the end effector in desired attitudes in a learning mode, or via indirect programming (“off-line programming”), i.e. the creation of desired courses of the joint angles corresponding to the inverse kinematics of the desired end effector attitudes.
The attitude represents a position and/or orientation of the end effector that, for example, can be described by a vector xεRn of the dimension n. For example, the path of the end effector can then be parameterized via a path parameter s (x=x(s)) that the manipulator executes in normal operation corresponding to a time profile ds/dt(t) so that the end effector travels the path with a corresponding path velocity dx/dt.
Since manipulators—in particular industrial and lightweight construction robots such as the robots of LBR I-IV series from the German Center for Air and Space Travel (DLR)—can travel very quickly in normal operation, and this hinders a direct examination of a path or a prompt manual emergency stop given incorrect paths. It is known for the operator to manually change (for example to reduce) the path velocity during the travel of the path in order to examine specific path segments or to test the interaction with other manipulators. The dynamic limits of the manipulator can be successively checked out by increasing the path velocity beyond normal operation in a targeted manner.
This change of the path velocity during the operation (“override”) has previously been entered into the controller of the manipulator manually via an operating element at a monitoring board. However, this is complicated, in particular when an operator wants to examine a joining process of a robot that is not in proximity, for example, and for this wants to correspondingly decrease the path velocity. In this case he must operate the operating element manually.
In addition or as an alternative to the path velocity, it can be desirable to also vary other process variables of the a manipulator and/or the process to be implemented by it. For example, given direct programming of a joining or welding process a contact pressure force of the manipulator or, respectively, a welding current at a work point should be adjustable by the operator.